FIG. 1 shows a configuration disclosed in Patent Literature 1 as a conventional example of a resolver device. The resolver device includes a resolver 11 that detects a rotation angle of the rotor, an excitation unit 12 that applies an excitation signal to the resolver 11, an output signal conversion unit 13 that converts the output signals of the resolver 11 to digital signals, and a computation unit 14 that corrects the rotation angle of the resolver 11 by using converted phase information of the resolver 11.
The resolver 11 is of a 1-phase excitation and 2-phase output type; both the output signals (SIN signal, COS signal) and the excitation signal are input to the output signal conversion unit 13; and the output signal conversion unit 13 generates digital signals that indicate phase information and zero-point information, from the excitation signal, the SIN signal, and the COS signal. The phase information and the zero-point information are input to the computation unit 14. The phase information contains an error relative to the actual rotation angle of the rotor.
FIG. 2 is a block diagram showing a control block of the computation unit 14. The computation unit 14 includes an error information table 20, an initialization processing unit 21, a revolution determination unit 22, a rotation period calculation unit 23, a uniform-velocity-rotation determination unit 24, a predicted rotation angle calculation unit 25, a resolver error calculation unit 26, and a corrected rotation angle calculation unit 27.
The error information table 20 can store a resolver error θe, which is the difference between a predicted rotation angle θp and the rotation angle θr in the phase information obtained while the resolver 11 is rotating at a uniform velocity, for each rotation angle of the resolver 11, and the initialization processing unit 21 sets the initial value of the resolver error θe in the error information table 20.
The revolution determination unit 22 determines from a pulse signal of zero-point information whether the number of revolutions of the resolver 11 is greater than or equal to a predetermined number of revolutions, the rotation period calculation unit 23 calculates the rotation period, and the uniform-velocity-rotation determination unit 24 determines whether the resolver 11 is rotating at a uniform velocity. The predicted rotation angle calculation unit 25 calculates the predicted rotation angle θp while the resolver 11 is rotating at a uniform velocity.
The resolver error calculation unit 26 calculates the resolver error θe while the resolver 11 is rotating at a uniform velocity, subjects the calculated resolver error θe to low-pass filtering, and updates the error information table 20. The resolver error θe is calculated for each rotation angle of the resolver 11.
The corrected rotation angle calculation unit 27 calculates a corrected rotation angle θa of the resolver 11 by adding or subtracting the resolver error θe stored in the error information table 20 to or from the rotation angle θr in the phase information. The corrected rotation angle θa is calculated for each rotation angle of the resolver 11. The calculated corrected rotation angle θa is output to a power converter 15. In FIG. 2, a reference numeral 16 denotes a motor driven by the power converter 15.